Abstract
The Mekong delta is experiencing rapid environmental change due to anthropogenic activities causing accelerated subsidence, sea-level rise and sediment starvation. Consequentially, the delta is rapidly losing elevation relative to sea level. Designating specific areas for sedimentation is a suggested strategy to encourage elevation-building with nature in deltas. We combined projections of extraction-induced subsidence, natural compaction and global sea-level rise with new projections of fluvial sediment delivery to evaluate the potential effectiveness of sedimentation strategies in the Mekong delta to 2050. Our results reveal that with current rates of subsidence and sediment starvation, fluvial sediments alone can only preserve elevation locally, even under optimistic assumptions, and organic sedimentation could potentially assume a larger role. While sedimentation strategies alone have limited effectiveness in the present context, combined with enhanced organic matter retention and interventions reducing anthropogenic-accelerated subsidence, they can considerably delay future relative sea-level rise, buying the delta crucial time to adapt.
Highlights
The Mekong delta is experiencing rapid environmental change due to anthropogenic activities causing accelerated subsidence, sea-level rise and sediment starvation
The example areas provide a range of sedimentation strategy scenarios, encompassing different extents, elevations and locations
Land surface elevation change relative to sea level in the Mekong delta depends on three main factors (Fig. 5): i) accumulation of new sediments through fluvial sediment deposition and in situ organic matter production increases surface elevation, ii) land subsidence, at delta scale predominantly caused by natural compaction of shallow sediments and aquifer-system compaction following groundwater overexploitation, results in surface elevation lowering, and iii) global, or climate change-induced, sea-level rise[46]
Summary
The Mekong delta is experiencing rapid environmental change due to anthropogenic activities causing accelerated subsidence, sea-level rise and sediment starvation. We present four examples of potential sedimentation areas (Fig. 2) and quantify the elevation change following targeted sedimentation strategies, including organic accumulation, using new delta elevation data[13], until 2050 under a range of environmental change scenarios.
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